Selfie picture shows Swiss pioneer Bertrand Piccard during the last leg of the round the world trip with Solar Impulse 2 over the Arab peninsula July 25, 2016. (Photo by Jean Revillard/Bertrand Piccard/Reuters/SI2)

Solar Impulse 2, the solar powered plane, piloted by Swiss pioneer Bertrand Piccard, is seen before landing in Abu Dhabi to finish the first around the world flight without the use of fuel, United Arab Emirates, July 26, 2016. (Photo by Jean Revillard/Bertrand Piccard/Reuters/SI2)

German test pilot Markus Scherdel steers the solar-powered Solar Impulse 2 aircraft with the Mont-Blanc in background during a training flight at its base in Payerne, September 27, 2014. (Photo by Denis Balibouse/Reuters)

German test pilot Markus Scherdel steers the solar-powered Solar Impulse 2 aircraft over the Lake Neuchatel during a training flight at its base in Payerne, September 27, 2014. (Photo by Denis Balibouse/Reuters)

Solar Impulse 2, a solar-powered plane piloted by Bertrand Piccard of Switzerland, flies over the Golden Gate bridge in San Francisco, California, U.S. April 23, 2016, before landing on Moffett Airfield following a 62-hour flight from Hawaii. (Photo by Jean Revillard/Reuters/Solar Impulse)

Picture taken by Swiss adventurer Andre Borschberg onboard Solar Impulse 2 (Si2) during the flight from Tusla/OK to Dayton/OH shows the Mississippi river at sunset, May 21, 2016. (Photo by Andre Borschberg/Jean Revillard/Christophe Chammartin/Reuters/SI2)

A bird flies along with the Solar Impulse as it approaches the runway for a landing following a test flight at Moffett Field in Mountain View, California April 19, 2013. (Photo by Robert Galbraith/Reuters)

A view of the Solar Impulse 2 on flight after taking off from Al Bateen Airport in United Arab Emirates, in this handout picture provided to Reuters, courtesy of Jean Revillard, on March 9, 2015. (Photo by Jean Revillard/Reuters/Solar Impulse)

Solar Impulse 2, the solar airplane, piloted by Swiss adventurer Andre Borschberg, flies over Manhattan, U.S. on June 11, 2016 shortly before landing at John F. Kennedy airport. Leg 14 was the shortest so far on the planes trip around the globe. (Photo by Andre Borschberg/Jean Revillard/Reuters/SI2)

The Solar Impulse 2 plane is seen on a maintenance flight over Hawaii performed by the test pilot Markus Scherdel in a handout picture taken March 27, 2016, and released April 14, 2016. (Photo by Jean Revillard/Reuters/Solar Impulse)

A handout picture made available by Solar Impulse on 26 July 2016, and shot by Swiss pilot Bertrand Piccard, shows Solar Impulse 2 (Si2) during its flight over the Red Sea, 24 July 2016, in the last leg of the Round-The-World journey as it heads to Abu Dhabi, UAE. Swiss long-range experimental solar-powered aircraft Si2 started its round-the-world solar flight from Abu Dhabi on 09 March 2015 and successfully completed it by returning to Abu Dhabi on 26 July 2016. (Photo by Jean Revillard/Bertrand Piccard/EPA)

Solar Impulse 2, the solar powered plane, piloted by Swiss pioneer Bertrand Piccard, lands in Abu Dhabi to finish the first around the world flight without the use of fuel, United Arab Emirates July 26, 2016. (Photo by Jean Revillard/Bertrand Piccard/Reuters/SI2)

Solar Impulse 2, a solar powered plane, arrives at an airport in Abu Dhabi, United Arab Emirates July 26, 2016. (Photo by Reuters/Stringer)

The Solar Impulse 2 aircraft, piloted by Bertrand Piccard, makes its final approach for landing at Al Batin Airport in Abu Dhabi to complete its world tour flight on July 26, 2016 in the United Arab Emirates. Solar Impulse 2 landed July 26 in the UAE, completing its epic journey to become the first sun-powered airplane to circle the globe without a drop of fuel to promote renewable energy. (Photo by Karim Sahib/AFP Photo)